U.S. patent number 5,667,512 [Application Number 08/642,696] was granted by the patent office on 1997-09-16 for patellar resection guide.
This patent grant is currently assigned to Metagen, LLC. Invention is credited to Wesley Johnson.
United States Patent |
5,667,512 |
Johnson |
September 16, 1997 |
Patellar resection guide
Abstract
A patella resection guide. The guide includes a cradle having
spaced cradle supports to support the quadriceps tendon and patella
ligament and properly locate the patella. The resection guide also
may have opposed, movable plates between which may be gripped
lateral and medial surfaces of a patella. One of the plates may
include a saw guide for guiding a bone saw in a resection
procedure. The guide may employ manually operable threaded
connections to facilitate drawing the plates together to grip
between them a patella to be resected.
Inventors: |
Johnson; Wesley (Chanhassen,
MN) |
Assignee: |
Metagen, LLC (Menomonie,
WI)
|
Family
ID: |
24577641 |
Appl.
No.: |
08/642,696 |
Filed: |
May 3, 1996 |
Current U.S.
Class: |
606/88;
606/87 |
Current CPC
Class: |
A61B
17/158 (20130101) |
Current International
Class: |
A61B
17/14 (20060101); A61B 17/15 (20060101); A61B
017/56 () |
Field of
Search: |
;606/79,86,87,88 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buiz; Michael
Assistant Examiner: Reip; David O.
Attorney, Agent or Firm: Fredrikson & Byron, PA
Claims
I claim:
1. A patella resection guide comprising a body, a pair of parallel
cradle surfaces carried by the body and spaced in the
superior-inferior direction so as to encounter and support
respective posterior surfaces of the quadriceps tendon and the
patella ligament of a patella received between the cradle surfaces,
the cradle surfaces defining a reference plane, and means for
resecting the patella at a desired orientation with respect to said
reference plane.
2. The patella resection guide of claim 1 wherein said cradle
surfaces are straight in the lateral-medial direction.
3. The patella resection guide of claim 1 wherein said cradle
surfaces are curved in the lateral-medial direction.
4. The patella resection guide of claim 1 wherein said body
includes adjustment means enabling the cradle surfaces to be moved
toward and away from each other while preserving their parallel
orientation.
5. The patella resection guide of claim 1 wherein the cradle
surfaces each include a straight central portion and end portions
angled from the central portion to retain between them and in
contact with the central portion the posterior surfaces of the
quadriceps tendon and patellar ligament, respectively.
6. The patella resection guide of claim 1 including a pair of
gripping elements carried by the body and movable toward each other
to firmly grip a patella between them.
7. The patella resection guide of claim 6 wherein said gripping
elements define between them a plane parallel to the plane defined
by said cradle surfaces.
8. The patella resection guide of claim 6 including manually
operable means for controllably drawing said gripping surfaces
toward each other.
9. The patella resection guide of claim 8 wherein said body
includes a plurality of guide rods extending between the gripping
elements and joining the gripping elements to the body and enabling
one gripping element to slide along the rods toward the other
gripping element.
10. The patella resection guide of claim 9 wherein said means for
drawing said gripping elements toward each other comprises a first
threaded element carried by one of the gripping elements and a
second threaded element carried by the other gripping element and
threadingly engaging the first threaded element, one of said
threaded elements being rotatable with respect to the other to draw
the gripping elements toward each other.
11. A patella resection guide comprising gripping means including a
pair of gripping elements having respective parallel confronting
gripping surfaces spaced to receive and grip a patella between
them, means for supporting said elements and retaining their
gripping surfaces in parallel while enabling them to be advanced
toward each other to grip a patella between them, at least one of
the gripping elements including saw guide means for guiding a bone
saw during resection of a patella gripped between the gripping
surfaces.
12. The patella resection guide of claim 11 including means for
controllably drawing said gripping elements toward each other.
13. The patella resection guide of claim 12 wherein said means for
drawing said gripping elements toward each other comprises a first
threaded element carried by one of the gripping elements and a
second threaded element carried by the other gripping element and
threadingly engaging the first threaded element, one of said
threaded elements being rotatable with respect to the other to move
the gripping elements toward and away from each other.
14. The patella resection guide of claim 13 wherein one of said
threaded elements comprises a rod having a threaded portion along
its length and the other threaded element comprises an interiorly
threaded nut, one of the rod and nut being non-rotatably attached
to one of the gripping elements and the other of the rod and nut
being rotatably mounted to the other gripping element.
15. The patella resection guide of claim 14 wherein one of said
gripping elements is recessed to rotatably receive said nut.
16. The patella resection guide of claim 15 wherein the rotatable
nut includes an outwardly extending manually rotatable adjustment
knob.
17. The patella resection guide of claim 11 wherein said means for
supporting said gripping elements includes a plurality of guide
rods extending between the gripping elements and enabling one
gripping element to slide along the rods toward the other gripping
element.
18. The patella resection guide of claim 11 wherein one or both of
said gripping surfaces include a plurality of teeth oriented to
contact and grip a patella received between the gripping
elements.
19. The patella resection guide of claim 11 wherein said saw blade
guide comprises one or more saw blade-receiving slots formed in one
or both of said gripping elements.
20. The patella resection guide of claim 11 including means
defining a pair of spaced, parallel, transversely extending cradle
surfaces positioned adjacent ends of said gripping elements to
encounter and support posterior surfaces of the quadriceps tendon
and the patella ligament, respectively, of a patella received
between the gripping elements.
21. A patella resection guide comprising a pair of gripping
elements having respective confronting gripping surfaces spaced to
receive a patella between them, means defining a pair of spaced,
parallel, transversely extending cradle surfaces positioned
adjacent ends of said gripping elements to encounter and support
posterior surfaces of the quadriceps tendon and the patellar
ligament, respectively, of a patella and to accurately position a
patella received between the gripping surfaces, means for
controllably drawing said gripping elements toward each other, and
means for supporting said gripping elements to maintain their
gripping surfaces in a parallel orientation while the gripping
elements are drawn toward each other to grip a patella between
them, at least one of the gripping elements including saw guide
means for guiding a bone saw during resection of a patella gripped
between the gripping elements.
22. A patella resection guide comprising a body, a pair of parallel
cradle surfaces carried by the body and spaced in the
superior-inferior direction so as to encounter and support
respective posterior surfaces of the quadriceps tendon and the
patella ligament of a patella received between the cradle surfaces,
gripping means comprising gripping elements having patella-gripping
surfaces in a confronting orientation, said gripping elements being
carried by said body and movable toward each other while
maintaining the confronting orientation of said gripping surfaces
to firmly grip between them lateral and medial surfaces of a
patella supported between said cradle surfaces, manually operable
means for controllably drawing said gripping elements toward each
other, and a saw guide carried by the gripping means for guiding a
bone saw during resection of a patella gripped by the gripping
means.
23. Method for resetting a patella, comprising:
a. surgically exposing the patella, quadriceps tendon and patellar
ligament;
b. providing a resection guide having parallel cradle surfaces
spaced to encounter posterior surfaces of the quadriceps tendon and
the patellar ligament of the patella to support a patella in a
fixed orientation with respect to a reference plane defined by said
cradle surfaces, means for gripping and holding the patella in said
fixed orientation,
c. supporting the patella in said resection guide with said cradle
surfaces contacting and supporting respectively the posterior
surfaces of the quadriceps tendon and the patellar ligament of the
patella,
d. gripping the patella in said orientation; and
e. resecting the patella.
24. The method of claim 23 including, before step d, flexing the
knee joint to draw the quadriceps tendon and patellar ligament
tightly against said cradle surfaces.
25. The method of claim 23 including, before step c, the step of
rotating the patella to expose its articular surface.
26. The method of claim 25 including, before step d, re-rotating
the patella to place the resection guide between the patella and
femur and flexing the knee joint to draw the quadriceps tendon and
patellar ligament tightly against said cradle surfaces.
27. The method of claim 23 or claim 26 including the step, before
step e, of rotating the patella to expose its articular surface to
facilitate said resection step.
28. The method of claim 23 wherein said resection guide includes a
bone saw guide, including the step of resecting the patella in a
plane in a resection operation in a plane having a predetermined
orientation to said reference plane.
29. Method for resecting a patella, comprising:
a. surgically exposing the patella, quadriceps tendon and patellar
ligament;
b. providing a resection guide having parallel cradle surfaces
spaced to encounter posterior surfaces of the quadriceps tendon and
the patellar ligament of the patella to support a patella in a
fixed orientation with respect to a reference plane defined by said
cradle surfaces, the resection guide having gripping surfaces
carried in opposed, confronting orientation by gripping elements
that are movable toward each other to encounter and grasp the
patella, and a saw guide,
c. supporting the patella in said resection guide with said cradle
surfaces contacting and supporting posterior surfaces of the
quadriceps tendon and the patellar ligament, respectively, of the
patella,
d. flexing the knee joint to draw the quadriceps tendon and
patellar ligament tightly against said cradle surfaces to position
the patella in said fixed orientation,
e. drawing said gripping elements together while maintaining the
opposed, confronting orientation of the gripping surfaces to grip
lateral and medial surfaces of the patella, and
f. resecting the patella with a saw guided by the saw guide.
Description
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for its use
during orthopaedic surgery. More particularly, it is directed to
apparatus and methods used to enable a surgeon to precisely resect
or trim a patella in connection with knee joint replacement
procedures.
BACKGROUND OF THE INVENTION
Surgical procedures to replace a complete or partial knee joint
with a prosthetic implant are becoming increasingly common, with
high rates of success. Total joint replacement is usually performed
to relieve pain and restore function caused by damaged or
malfunctioning joints.
In addition to replacing the diseased natural knee with femoral and
tibial prostheses, the knee joint replacement procedure typically
involves resurfacing the articular surface of the patella because
in some cases the natural bone of the patella does not interface
well with the materials used in constructing the prosthesis, and
this can result in great pain to the patient. In most cases, the
patella is resurfaced with a prosthetic component, or patellar
button which may be made from ultra high molecular weight
polyethylene.
Implantation of resurfacing components to the patella, in
combination with the prosthetic knee joint if improperly aligned,
can result in an undesirable alteration of the load distribution
imparted to the prosthesis and supporting bone structures. Normal
daily activity, such as walking, causes flexion and extension of
the quadriceps mechanism, patellar ligament, and associated
tendons. These movements in turn exert loads on the attached and
surrounding anatomical or prosthetic structures.
In total knee joint replacement, it is critical to achieve uniform
and properly oriented load transfer from the implant to the
supporting bone. To accomplish this, it is desirable to recreate
the loading patterns which are imparted to the supporting bone
prior to placing the implants, as occurs in a normal, naturally
functioning knee. These loading patterns are primarily compressive
and adverse bone remodelling can result if atypical loading
patterns, including shear, are introduced in the total knee
procedure. It is thus desirable to accurately orient the implants
to recreate normal stress patterns in supportive bony structure.
When the patella is properly resected, the resultant force active
on the patella will be generally perpendicular to the main plane of
the patella, resulting in primarily compressive forces being
imparted to the supporting bone. In this manner, the desired
loading patterns may be recreated, imparting primarily compressive
loads on the supporting bone to imitate the normal, natural
condition.
Several devices are known in the prior art for resecting the
articular surface of the patella. These commonly involve pliers or
scissors-like mechanisms which grasp the patella. The surgeon is
required to orient the patella in the device by visual
approximation, relying on judgment for proper positioning and
orientation. Available resection guides do not provide a reference
to bony or soft tissue structures. The patella is then resected by
placing a saw through the resection guide and sawing the patella.
In the event of inaccurate or improper orientation of the patella
within the device, the depth or angle of resection will be
incorrect. This will result in an improper distribution of forces
to the new knee joint, and adverse loading of the supporting bone
structures may result.
What is clearly needed, therefore, is a device and method which
will aid the surgeon in establishing an accurate and repeatable
orientation of the patella during a resection procedure so as to
enable proper orientation of a subsequently implanted patellar
implant.
SUMMARY OF THE INVENTION
The present invention makes use of a device which is capable of
offering the surgeon great precision, simplicity and reliability in
resecting or trimming the patella as required in knee replacement
surgery. In one embodiment, the invention provides a patella
resection guide comprising a body carrying a pair of parallel
cradle surfaces spaced so as to encounter and support respectively
the posterior surfaces of the quadriceps tendon and the patella
ligament of a patella received between the cradle surfaces. The
parallel cradle surfaces define a reference plane, and the
resection guide includes means for resecting the patellar at a
desired orientation with respect to the reference plane.
In another embodiment, the invention comprises a patella resection
guide that comprising gripping means including a pair of gripping
elements having respective confronting gripping surfaces spaced to
receive and grip a patella between them. Means are provided for
supporting the gripping elements and maintaining the orientation of
the gripping surfaces while enabling them to be advanced toward
each other to grip a patella between them. At least one of the
gripping elements includes saw guide means for guiding a bone saw
during resection of a patella gripped between the gripping
surfaces.
In a specific embodiment, the invention comprises a cradle designed
to support posterior surfaces of the quadriceps tendon and patellar
ligament during resection procedures. The cradle also acts as a
frame to mount the gripping elements and permit them to move
together and apart. Different sized cradles and plates are
contemplated and within the scope of the invention. On either side
of the cradle and opposing each other are the gripping elements
which may be in the form of movable plates which act to secure the
patella in the device. Means are also provided to advance or
retract, and to secure and lock the position of the plates.
In yet another embodiment, the invention relates to a method for
resecting a patella in which the patella, quadriceps tendon and
patellar ligament are first surgically exposed. A resection guide
is provided, the guide including a saw blade guide such as a slot.
The resection guide has parallel cradle surfaces defining a
reference plane and spaced to encounter posterior surfaces of the
quadriceps tendon and the patella ligament of the patellar to
support the patella in a fixed orientation with respect to the
reference plane. The resection guide includes means for gripping
and holding the patella in that orientation. In the method of this
embodiment, the patella is supported in the resection guide with
the cradle surfaces contacting and supporting respectively the
posterior surfaces of the quadriceps tendon and patellar ligament.
The patella is then gripped in that orientation, and the patella is
resected with a bone saw guided by the saw guide.
In a preferred embodiment, the patella is resurfaced in the course
of performing total knee replacement surgery. An incision is made
which runs medial to the patella and which exposes the patella and
attached quadriceps tendon and patella ligament structures. The
patellofemoral joint is disarticulated, following which the patella
is rotated laterally. This exposes the inner or articular surface
of the patella. Next, the patellar resection guide of the invention
is placed over the exposed articular surface of the patella. When
this step is complete, the patella and resection guide together are
reversed again, the patella being suspended between the parallel
cradle supporting surfaces.
At this point, the guide is positioned between the patella and the
femur, with the patellar ligament and quadriceps tendon suspended
in the cradle support of the patellar resection guide. The knee is
then slightly bent to draw the posterior surfaces of the quadriceps
tendon and ligament firmly against the cradle surfaces and into the
resection guide. The gripping elements are then drawn toward each
other, firmly securing between them the patella. With the patella
thus secured, the patella and guide are re-rotated to expose the
articular surface of the patella. The resection procedure is
performed at this stage through the use of an oscillating saw
guided by the saw guide. Following resection of the patella and
removal of the resection guide, established procedures may be
followed to prepare the resected surface of the patella for
reception of an implant or patellar button.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, partially exploded, of a patellar
resection guide of the present invention;
FIG. 2 is a top view of the assembled patellar resection guide of
FIG. 1;
FIG. 3 is an end view of the patellar resection guide of FIG.
1;
FIG. 4 is a side view of the patellar resection guide of FIG.
1;
FIG. 5 is a perspective view of a cradle of the patellar resection
guide shown in FIGS. 1-4;
FIG. 6 is a perspective view of a modified cradle;
FIG. 7 is a front end view of an embodiment of a bone guide plate
of the patellar resection guide of FIG. 1 with a plurality of saw
blade slots;
FIG. 8 is a front end view similar to FIG. 7 showing a bone guide
plate with an alternate arrangement of saw blade slots;
FIG. 9 is a side view of a stop plate showing an adjustment bolt
and guide rods;
FIG. 10 is a side view of a captured adjustment nut employed in the
patellar resection guide of FIG. 1;
FIG. 11 is a bottom view of a blade guide plate showing a T shaped
channel to accommodate the removable captured nut shown in FIG.
10;
FIG. 12 is a front view of the stop plate of the patellar resection
guide of FIG. 1;
FIG. 13 shows a diagrammatic side view of the patellar resection
guide of FIG. 1 as used during a surgical procedure; and
FIGS. 14 and 15 are diagrammatic views showing steps in a surgical
method using the resection guide of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference first to FIG. 1, a patellar resection guide is
designated 10, and comprises a cradle 12 and a pair of gripping
elements such as plates 14, 20. The cradle 12 is used to suspend
the patella in a desired orientation established by supporting
posterior surfaces of the quadriceps tendon and patellar ligament
between the surfaces of spaced, parallel first and second cradle
supports 30, 31, locating the articular surface of the patella in a
position where it can be accessed by the surgeon's bone saw blade
for resection.
The gripping plates comprise a blade guide plate 14 and a stop
plate 20, both generally rectangular in shape and having patella
gripping surfaces 21, 23. The gripping plates are sized and
positioned to fit between the cradle supports 30, 31 to permit
adjustable positioning of the distance between their respective
gripping surfaces. The cradle supports 30, 31 are joined by a body
defined by cross members 29. An adjustment bolt 16 passes through
an aperture 36 in the cross members 29 of the cradle 12, as do two
guide rods 17 arranged in parallel with the adjustment bolt 16. One
or more saw blade slots 24 are formed through the blade guide plate
14 at positions designed to represent the proper depth required for
resecting the articular surface of the patella.
Stop plate 20 is positioned with its gripping surface 21 opposed to
and confronting the gripping surface 23 of the guide plate 14, the
surfaces 21 and 23 desirably being parallel. Adjustment bolt 16
passes through the apertures 36 in the cross members 29 of the
cradle 12, and guide rods 17 pass snugly through the apertures 34
in the cross members 29 and through the apertures 35 in the blade
guide plate 14 to allow for controlled, supportive convergent and
divergent travel of the blade guide plate 14 and stop plate 20.
Blade guide plate similarly possesses an aperture 33 sized to
receive adjustment bolt 16. Stop plate 20 is of similar size and
shape to the blade guide plate 14, but may or may not contain a
slot for guiding a saw blade. Stop plate 20 may be shallower in
depth than blade guide plate 14. Adjustment bolt 16 and guide rods
17 are rigidly affixed to the stop plate 20. Adjustment bolt 16 is
threaded from the portion extending from its free end to a point
toward the stop plate 20 where the size limitations of the patella
or cradle 12 obviate the need for further threading. When the stop
plate 20 and affixed adjustment bolt 16 and affixed guide rods 17
are fitted through apertures 36, 34 in the cross members 29 forming
the base of cradle 12, the blade guide plate 14 confront each
other, as shown in FIG. 1.
Referring to FIG. 11, the blade guide plate 14 has a T shaped
channel 15 cut into its bottom side to receive a nut 19 that is
threaded onto the adjustment bolt 16. The nut is restrained by the
walls of the crossbar portion of the T channel from movement
parallel to its axis, and includes a tubular portion exuding
through the leg of the T and terminating in an external, preferably
knurled handle 25. Manual rotation of the handle 25 rotates the nut
upon the threaded portion of the bolt to cause the blade guide
plate 14 and stop plate 20 to be selectively moved toward and away
from each other to accommodate and secure various sized patellae
which may be encountered. The guide rods 17 ensure parallel
movement of the blade guide plate 14 and stop plate 20. The
gripping surfaces 21, 23 of the blade guide plate 14 and stop plate
20 may be provided with teeth 18, 22 or other irregular surfaces to
facilitate grasping of the patella during the resection
procedure.
As shown in FIG. 5, the supports 30, 31 have at their distal ends
angled end portions that define end stops 32, the latter preferably
being substantially at right angles to the cradle supports 30, 31.
The cradle supports 30, 31 are connected in a substantially
perpendicular manner to upright members 28. The upright members 28
are connected at substantially right angles to cross members 29.
Cradle 12 is substantially symmetrical in configuration and serves
as the framework for the other components of the invention. The
patellar resection guide 10 quickly disassembles for easy cleaning
or replacement of components.
Cradle 12 is provided with apertures 34, 36 which are adapted so as
to slidably receive the guide rods 17. Aperture 36 is adapted to
slidably receive adjustment bolt 16. Apertures 34, 36 are sized to
allow blade guide plate 14 and stop plate 20 to adjust the distance
from each other which will occur with rotating the adjustment nut
16. Tolerances between apertures 34, 36 and the respective guide
rods 17 and adjustment bolt 16 should be great enough to allow free
movement, but close enough to prevent unnecessary looseness during
the operation of the patellar resection guide and to maintain the
plates in their parallel orientation as they are drawn
together.
The cradle supports 30, 31 are on opposite ends of the cradle 12
and desirably are parallel to each other; that is, they have outer
surfaces 48, 50 that are congruent to each other. Support surfaces
48, 50 may be slightly curved (concave outwardly), but preferably
are straight in the medial-lateral direction to define between them
a reference plane. They are used to suspend the quadriceps tendon
and patella ligament in a plane which is parallel to but not
necessarily coplanar with the desired resection plane. The distance
between cradle supports 30, 31 is sufficient to accommodate between
them a human patella with the posterior surfaces of the attached
quadriceps tendon and patellar ligament resting on the cradle
supports. Desirably, the spacing between the cradle supports is
slightly greater than the superior-inferior dimension of the
patella so that when the patella is drawn between the cradle
supports as by flexing the knee, the supports do not contact the
patella itself. In a preferred embodiment, the end-to-end dimension
of the gripping plates is sufficiently small as to enable the
plates to fit between cradle supports separated by varying
distances. In this manner, the resection guide is modular in
construction so that a cradle of any particular chosen size can be
assembled with a standard sized pair of gripping plates. Of course,
if desired, gripping plates of varying dimensions can be supplied
as well.
While is desired that the gripping means be so oriented as to grip
the lateral and medial surfaces of a patella received between the
cradle support surfaces, the gripping elements may instead be
provided by the cradle structure so that the cradle supports may be
moved toward each other to capture between them the patella. FIG. 6
shows an embodiment in which the frame structure supporting the
cradles is itself adjustable to enable the cradles to move toward
and away from each other while maintaining their mutually parallel
orientation. In FIG. 6, each of the cradle cross members 29 is
formed with telescoping ends, one end 38 of each cross member being
telescopingly received in the adjacent hollow end 40. Set screws 42
may be used to join the ends 38, 40 together once the correct
length of these members has been set. The confronting surfaces 44,
46 of the respective cradle supports 30, 31 may serve as gripping
surfaces (and may be provided with teeth or the like) to grip
between them a patella, the quadriceps tendon and patellar ligament
of which rest against the outer support surfaces 48, 50 of the
cradle supports. Saw blade guiding surfaces or slots (not shown)
may be provided to guide a saw blade.
FIGS. 7 and 8 show an embodiment of the blade guide plate 14 having
a plurality of saw blade guide slots 24. The saw blade slots 24 as
shown illustrate how the invention is able to accommodate various
depths of resection the surgeon may require due to differing sized
patellae or conditions. In addition to providing a variety of
resection depths, the blade guide plate 14 must also provide
stability and orientation to the oscillating saw blade to ensure
that the resection is done in the proper plane. This is
accomplished by employing a slot depth sufficient to prevent
significant tilting of the saw blade during the resection
procedure. Slot depth dimensions of approximately 0.25 inch to 0.5
inches have been shown to be adequate for this purpose. These
dimensions, however, are intended to be illustrative and not
limiting.
Although the invention is described primarily with respect to
resection using a bone saw to form a planar posterior surface on
the patella, it will be understood that the patella may be resected
by forming holes, grooves or other shapes in or on the posterior
patellar surface. The end-to-end length of the blade guide plate 14
and stop plate 20 are less than the distance between the cradle
supports 30, 31 to enable blade guide plate 14 and stop plate 20 to
move toward each other sufficiently close to effectively grasp the
patella during the resection procedure. It is contemplated and
within the scope of this invention to manufacture the cradle 12 in
various sizes, to be able to accommodate differently sized
patellae. Similarly, blade guide plate 14 and stop plate 20 would
be sized to be able to be compatible with the contemplated
variously sized cradles 12.
FIG. 9 shows the stop plate 20 with rigidly affixed guide rods 17
and adjustment bolt 16. When assembling the patellra resection
guide 10, the stop plate 20, adjustment bolt 16 and guide rods 17
are first fitted through the apertures 36, 34 in the cross members
29 of the cradle 12. Following this, the captured nut 19 is fitted
into the T shaped channel 15 of the blade guide plate 14. The
captured nut 19 is best shown in FIG. 10, and the T shaped channel
15 of the bone guide plate 14 is best shown in FIG. 11. Next, the
adjustment bolt 16 and guide rods 17 are placed through the
apertures 33, 35 of the blade guide plate 14. It is necessary to
align the captured nut 19 with the adjustment bolt 16 and then turn
the captured nut 19 in a direction corresponding with advancing the
blade guide plate 14 toward the stop plate 20. At this point,
assuming it is properly sterilized, the patellar resection guide 10
is assembled and ready for use.
It is also contemplated to assemble and use the blade guide plate
14 and stop plate 20 without the cradle 12. This embodiment would
give the surgeon somewhat greater flexibility in resecting the
patella, but a lesser degree of precision.
FIG. 12 shows the stop plate 20 and affixed adjustment bolt 16 and
guide rods 17 prior to assembly.
The preferred material for all components of this invention is
stainless steel. Other materials, including but not limited to
other metals and metal alloys, plastics and composite materials,
are also anticipated as being appropriate.
FIG. 13 shows the patellar resection guide 10 as it would be used
during an actual procedure. It can be seen that the quadriceps
tendon T and patellar ligament L are suspended in a plane defined
by first cradle support 30 and second cradle support 31 of the
cradle 12. The patella P is secured in the patellar resection guide
10 by means of force exerted by the gripping surfaces 21, 23.
Flexion of the knee joint causes the quadriceps tendon T and
patellar ligament L to press against the cradle supports, properly
orienting the patella between the gripping plates before they are
moved to their gripping position. The procedure for using the guide
is discussed in detail below.
In a typical procedure for using the patellar resection guide, the
surgeon first creates a longitudinal incision medial to the patella
to expose the patella and quadriceps mechanism which includes the
quadriceps tendon and patellar ligament. This is done to a degree
allowing exposure of sufficient quadriceps tissue and patellar
ligament to permit the surgeon to rotate the patella laterally
prior to insertion of the resection guide 10. As shown in FIG. 14,
the patella is disarticulated from the femur and is turned upside
down, that is, it is rotated laterally through about 180.degree.,
resulting in the articular surface A of the patella facing forward
or anteriorly (that is, outwardly).
At this point, the surgeon places the patellar resection guide 10
over the exposed articular surface of the patella, with the cradle
supports adjacent the quadriceps tendon and patellar ligament. The
patella and patellar resection guide together are re-rotated
medially through about 180.degree. to position the resection guide
10 between the patella and the femur. The knee is slightly flexed
to tension the quadriceps mechanism, thereby applying a compressive
load between the patella and femur. This draws the quadriceps
ligament and patella tendon firmly into the cradle supports of the
guide 10. When the patellar tendon and ligament are firmly seated
in the cradle 12, as shown in FIG. 13, the patella is positioned in
a repeatable or reference position with respect to the reference
plane defined by the cradle support surfaces. This position is
defined by the posterior aspect of the inferior and superior
margins of the ligament and tendon attachment of the patella,
respectively, which, when they are firmly seated against the
support surfaces, lie in the reference plane defined by the cradle
supports. This plane is typically perpendicular to the resultant
forces acting on the patella and is parallel to the plane of the
intended resection. The preferred orientation of the patellar
resection plane is perpendicular to the resultant forces acting
across the patellar femoral joint. While maintaining slight flexion
on the knee, the captured nut 19 is rotated in a direction causing
the blade guide plate 14 and stop plate 20 to move closer together.
The blade guide plate 14 and stop plate 20 move in a mediolateral
sense. This procedure is followed until the patella is securely
gripped in the patellar resection guide 10.
With the patella thus firmly gripped, the patella and resection
guide are again rotated laterally to again orient the resection
guide 10 and articular surface of the patella outwardly, as shown
in FIG. 15. The surgeon places an oscillating bone saw of a type
commonly known into the saw blade slot 24 and advances the saw to
resect the patella. The articular surface of the patella is
resected at a level posterior to the ligament and tendon
insertions. This permits the surgeon to resect only bone tissue,
avoiding the ligaments and tendons. The depth of resection beneath
the ligament and tendon insertion levels may vary depending on
surgeon preference. In one embodiment the invention accommodates
for this requirement by providing multiple saw blade slots 24 at
differing levels in the blade guide plate 14. In one embodiment, a
level of one millimeter is used. The level may range from a level
matching that of the ligament and tendon insertion level, to a
level posterior to it, or anterior to it.
Following resection, the patellar resection guide 10 is removed.
After removal of the guide 10, the surgeon will follow established
procedures to further prepare the resected articular surface of the
patella to accept a patellar button or other implant.
While a preferred embodiment of the present invention has been
described, it should be understood that various changes,
adaptations, and modifications may be made without departing from
the spirit of the invention and the scope of the claims.
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